Resonant and semi-resonant DC-DC converters, including isolated and non-isolated topologies, are used in a variety of applications such as telecommunications, processors, etc. because of their zero-voltage (current) switching characteristic and their ability to utilize parasitic components. Among numerous topologies, the semi-resonant converter with transformer/tapped-inductor is an attractive topology for high voltage conversion ratio without isolation. Lower cost and higher efficiency are the main advantages of such converters over other solutions.
The output current of many resonant and semi-resonant DC-DC converters has a half cycle sinusodial-like shape each switching cycle. Fixed frequency control may not be an efficient topology for such converters, so there is a need for variable switching frequency control to achieve optimal performance and provide soft switching for variable frequency operations.
As such, there is a need for variable switching frequency digital control for resonant and semi-resonant DC-DC converters having an output current with a sinusodial-like shape.